text: //===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // The file defines the MachineFrameInfo class.
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H
  #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
  
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/Support/DataTypes.h"
  #include <cassert>
  #include <vector>
  
  namespace llvm {
  class raw_ostream;
  class DataLayout;
  class TargetRegisterClass;
  class Type;
  class MachineFunction;
  class MachineBasicBlock;
  class TargetFrameLowering;
  class BitVector;
  class Value;
  class AllocaInst;
  
  /// The CalleeSavedInfo class tracks the information need to locate where a
  /// callee saved register is in the current frame.
  class CalleeSavedInfo {
    unsigned Reg;
    int FrameIdx;
  
  public:
    explicit CalleeSavedInfo(unsigned R, int FI = 0)
    : Reg(R), FrameIdx(FI) {}
  
    // Accessors.
    unsigned getReg()                        const { return Reg; }
    int getFrameIdx()                        const { return FrameIdx; }
    void setFrameIdx(int FI)                       { FrameIdx = FI; }
  };
  
  /// The MachineFrameInfo class represents an abstract stack frame until
  /// prolog/epilog code is inserted.  This class is key to allowing stack frame
  /// representation optimizations, such as frame pointer elimination.  It also
  /// allows more mundane (but still important) optimizations, such as reordering
  /// of abstract objects on the stack frame.
  ///
  /// To support this, the class assigns unique integer identifiers to stack
  /// objects requested clients.  These identifiers are negative integers for
  /// fixed stack objects (such as arguments passed on the stack) or nonnegative
  /// for objects that may be reordered.  Instructions which refer to stack
  /// objects use a special MO_FrameIndex operand to represent these frame
  /// indexes.
  ///
  /// Because this class keeps track of all references to the stack frame, it
  /// knows when a variable sized object is allocated on the stack.  This is the
  /// sole condition which prevents frame pointer elimination, which is an
  /// important optimization on register-poor architectures.  Because original
  /// variable sized alloca's in the source program are the only source of
  /// variable sized stack objects, it is safe to decide whether there will be
  /// any variable sized objects before all stack objects are known (for
  /// example, register allocator spill code never needs variable sized
  /// objects).
  ///
  /// When prolog/epilog code emission is performed, the final stack frame is
  /// built and the machine instructions are modified to refer to the actual
  /// stack offsets of the object, eliminating all MO_FrameIndex operands from
  /// the program.
  ///
  /// @brief Abstract Stack Frame Information
  class MachineFrameInfo {
  
    // StackObject - Represent a single object allocated on the stack.
    struct StackObject {
      // SPOffset - The offset of this object from the stack pointer on entry to
      // the function.  This field has no meaning for a variable sized element.
      int64_t SPOffset;
  
      // The size of this object on the stack. 0 means a variable sized object,
      // ~0ULL means a dead object.
      uint64_t Size;
  
      // Alignment - The required alignment of this stack slot.
      unsigned Alignment;
  
      // isImmutable - If true, the value of the stack object is set before
      // entering the function and is not modified inside the function. By
      // default, fixed objects are immutable unless marked otherwise.
      bool isImmutable;
  
      // isSpillSlot - If true the stack object is used as spill slot. It
      // cannot alias any other memory objects.
      bool isSpillSlot;
  
      // MayNeedSP - If true the stack object triggered the creation of the stack
      // protector. We should allocate this object right after the stack
      // protector.
      bool MayNeedSP;
  
      /// Alloca - If this stack object is originated from an Alloca instruction
      /// this value saves the original IR allocation. Can be NULL.
      const AllocaInst *Alloca;
  
      // PreAllocated - If true, the object was mapped into the local frame
      // block and doesn't need additional handling for allocation beyond that.
      bool PreAllocated;
  
      StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
                  bool isSS, bool NSP, const AllocaInst *Val)
        : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
          isSpillSlot(isSS), MayNeedSP(NSP), Alloca(Val), PreAllocated(false) {}
    };
  
    /// Objects - The list of stack objects allocated...
    ///
    std::vector<StackObject> Objects;
  
    /// NumFixedObjects - This contains the number of fixed objects contained on
    /// the stack.  Because fixed objects are stored at a negative index in the
    /// Objects list, this is also the index to the 0th object in the list.
    ///
    unsigned NumFixedObjects;
  
    /// HasVarSizedObjects - This boolean keeps track of whether any variable
    /// sized objects have been allocated yet.
    ///
    bool HasVarSizedObjects;
  
    /// FrameAddressTaken - This boolean keeps track of whether there is a call
    /// to builtin \@llvm.frameaddress.
    bool FrameAddressTaken;
  
    /// ReturnAddressTaken - This boolean keeps track of whether there is a call
    /// to builtin \@llvm.returnaddress.
    bool ReturnAddressTaken;
  
    /// StackSize - The prolog/epilog code inserter calculates the final stack
    /// offsets for all of the fixed size objects, updating the Objects list
    /// above.  It then updates StackSize to contain the number of bytes that need
    /// to be allocated on entry to the function.
    ///
    uint64_t StackSize;
  
    /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
    /// have the actual offset from the stack/frame pointer.  The exact usage of
    /// this is target-dependent, but it is typically used to adjust between
    /// SP-relative and FP-relative offsets.  E.G., if objects are accessed via
    /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
    /// to the distance between the initial SP and the value in FP.  For many
    /// targets, this value is only used when generating debug info (via
    /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
    /// corresponding adjustments are performed directly.
    int OffsetAdjustment;
  
    /// MaxAlignment - The prolog/epilog code inserter may process objects
    /// that require greater alignment than the default alignment the target
    /// provides. To handle this, MaxAlignment is set to the maximum alignment
    /// needed by the objects on the current frame.  If this is greater than the
    /// native alignment maintained by the compiler, dynamic alignment code will
    /// be needed.
    ///
    unsigned MaxAlignment;
  
    /// AdjustsStack - Set to true if this function adjusts the stack -- e.g.,
    /// when calling another function. This is only valid during and after
    /// prolog/epilog code insertion.
    bool AdjustsStack;
  
    /// HasCalls - Set to true if this function has any function calls.
    bool HasCalls;
  
    /// StackProtectorIdx - The frame index for the stack protector.
    int StackProtectorIdx;
  
    /// FunctionContextIdx - The frame index for the function context. Used for
    /// SjLj exceptions.
    int FunctionContextIdx;
  
    /// MaxCallFrameSize - This contains the size of the largest call frame if the
    /// target uses frame setup/destroy pseudo instructions (as defined in the
    /// TargetFrameInfo class).  This information is important for frame pointer
    /// elimination.  If is only valid during and after prolog/epilog code
    /// insertion.
    ///
    unsigned MaxCallFrameSize;
  
    /// CSInfo - The prolog/epilog code inserter fills in this vector with each
    /// callee saved register saved in the frame.  Beyond its use by the prolog/
    /// epilog code inserter, this data used for debug info and exception
    /// handling.
    std::vector<CalleeSavedInfo> CSInfo;
  
    /// CSIValid - Has CSInfo been set yet?
    bool CSIValid;
  
    /// TargetFrameLowering - Target information about frame layout.
    ///
    const TargetFrameLowering &TFI;
  
    /// LocalFrameObjects - References to frame indices which are mapped
    /// into the local frame allocation block. <FrameIdx, LocalOffset>
    SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
  
    /// LocalFrameSize - Size of the pre-allocated local frame block.
    int64_t LocalFrameSize;
  
    /// Required alignment of the local object blob, which is the strictest
    /// alignment of any object in it.
    unsigned LocalFrameMaxAlign;
  
    /// Whether the local object blob needs to be allocated together. If not,
    /// PEI should ignore the isPreAllocated flags on the stack objects and
    /// just allocate them normally.
    bool UseLocalStackAllocationBlock;
  
    /// Whether the "realign-stack" option is on.
    bool RealignOption;
  public:
      explicit MachineFrameInfo(const TargetFrameLowering &tfi, bool RealignOpt)
      : TFI(tfi), RealignOption(RealignOpt) {
      StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
      HasVarSizedObjects = false;
      FrameAddressTaken = false;
      ReturnAddressTaken = false;
      AdjustsStack = false;
      HasCalls = false;
      StackProtectorIdx = -1;
      FunctionContextIdx = -1;
      MaxCallFrameSize = 0;
      CSIValid = false;
      LocalFrameSize = 0;
      LocalFrameMaxAlign = 0;
      UseLocalStackAllocationBlock = false;
    }
  
    /// hasStackObjects - Return true if there are any stack objects in this
    /// function.
    ///
    bool hasStackObjects() const { return !Objects.empty(); }
  
    /// hasVarSizedObjects - This method may be called any time after instruction
    /// selection is complete to determine if the stack frame for this function
    /// contains any variable sized objects.
    ///
    bool hasVarSizedObjects() const { return HasVarSizedObjects; }
  
    /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
    /// stack protector object.
    ///
    int getStackProtectorIndex() const { return StackProtectorIdx; }
    void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
  
    /// getFunctionContextIndex/setFunctionContextIndex - Return the index for the
    /// function context object. This object is used for SjLj exceptions.
    int getFunctionContextIndex() const { return FunctionContextIdx; }
    void setFunctionContextIndex(int I) { FunctionContextIdx = I; }
  
    /// isFrameAddressTaken - This method may be called any time after instruction
    /// selection is complete to determine if there is a call to
    /// \@llvm.frameaddress in this function.
    bool isFrameAddressTaken() const { return FrameAddressTaken; }
    void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
  
    /// isReturnAddressTaken - This method may be called any time after
    /// instruction selection is complete to determine if there is a call to
    /// \@llvm.returnaddress in this function.
    bool isReturnAddressTaken() const { return ReturnAddressTaken; }
    void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }
  
    /// getObjectIndexBegin - Return the minimum frame object index.
    ///
    int getObjectIndexBegin() const { return -NumFixedObjects; }
  
    /// getObjectIndexEnd - Return one past the maximum frame object index.
    ///
    int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
  
    /// getNumFixedObjects - Return the number of fixed objects.
    unsigned getNumFixedObjects() const { return NumFixedObjects; }
  
    /// getNumObjects - Return the number of objects.
    ///
    unsigned getNumObjects() const { return Objects.size(); }
  
    /// mapLocalFrameObject - Map a frame index into the local object block
    void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
      LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
      Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
    }
  
    /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
    std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
      assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
              "Invalid local object reference!");
      return LocalFrameObjects[i];
    }
  
    /// getLocalFrameObjectCount - Return the number of objects allocated into
    /// the local object block.
    int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
  
    /// setLocalFrameSize - Set the size of the local object blob.
    void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; }
  
    /// getLocalFrameSize - Get the size of the local object blob.
    int64_t getLocalFrameSize() const { return LocalFrameSize; }
  
    /// setLocalFrameMaxAlign - Required alignment of the local object blob,
    /// which is the strictest alignment of any object in it.
    void setLocalFrameMaxAlign(unsigned Align) { LocalFrameMaxAlign = Align; }
  
    /// getLocalFrameMaxAlign - Return the required alignment of the local
    /// object blob.
    unsigned getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }
  
    /// getUseLocalStackAllocationBlock - Get whether the local allocation blob
    /// should be allocated together or let PEI allocate the locals in it
    /// directly.
    bool getUseLocalStackAllocationBlock() {return UseLocalStackAllocationBlock;}
  
    /// setUseLocalStackAllocationBlock - Set whether the local allocation blob
    /// should be allocated together or let PEI allocate the locals in it
    /// directly.
    void setUseLocalStackAllocationBlock(bool v) {
      UseLocalStackAllocationBlock = v;
    }
  
    /// isObjectPreAllocated - Return true if the object was pre-allocated into
    /// the local block.
    bool isObjectPreAllocated(int ObjectIdx) const {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
    }
  
    /// getObjectSize - Return the size of the specified object.
    ///
    int64_t getObjectSize(int ObjectIdx) const {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      return Objects[ObjectIdx+NumFixedObjects].Size;
    }
  
    /// setObjectSize - Change the size of the specified stack object.
    void setObjectSize(int ObjectIdx, int64_t Size) {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      Objects[ObjectIdx+NumFixedObjects].Size = Size;
    }
  
    /// getObjectAlignment - Return the alignment of the specified stack object.
    unsigned getObjectAlignment(int ObjectIdx) const {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      return Objects[ObjectIdx+NumFixedObjects].Alignment;
    }
  
    /// setObjectAlignment - Change the alignment of the specified stack object.
    void setObjectAlignment(int ObjectIdx, unsigned Align) {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
      ensureMaxAlignment(Align);
    }
  
    /// getObjectAllocation - Return the underlying Alloca of the specified
    /// stack object if it exists. Returns 0 if none exists.
    const AllocaInst* getObjectAllocation(int ObjectIdx) const {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      return Objects[ObjectIdx+NumFixedObjects].Alloca;
    }
  
    /// NeedsStackProtector - Returns true if the object may need stack
    /// protectors.
    bool MayNeedStackProtector(int ObjectIdx) const {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      return Objects[ObjectIdx+NumFixedObjects].MayNeedSP;
    }
  
    /// getObjectOffset - Return the assigned stack offset of the specified object
    /// from the incoming stack pointer.
    ///
    int64_t getObjectOffset(int ObjectIdx) const {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      assert(!isDeadObjectIndex(ObjectIdx) &&
             "Getting frame offset for a dead object?");
      return Objects[ObjectIdx+NumFixedObjects].SPOffset;
    }
  
    /// setObjectOffset - Set the stack frame offset of the specified object.  The
    /// offset is relative to the stack pointer on entry to the function.
    ///
    void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      assert(!isDeadObjectIndex(ObjectIdx) &&
             "Setting frame offset for a dead object?");
      Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
    }
  
    /// getStackSize - Return the number of bytes that must be allocated to hold
    /// all of the fixed size frame objects.  This is only valid after
    /// Prolog/Epilog code insertion has finalized the stack frame layout.
    ///
    uint64_t getStackSize() const { return StackSize; }
  
    /// setStackSize - Set the size of the stack...
    ///
    void setStackSize(uint64_t Size) { StackSize = Size; }
  
    /// Estimate and return the size of the stack frame.
    unsigned estimateStackSize(const MachineFunction &MF) const;
  
    /// getOffsetAdjustment - Return the correction for frame offsets.
    ///
    int getOffsetAdjustment() const { return OffsetAdjustment; }
  
    /// setOffsetAdjustment - Set the correction for frame offsets.
    ///
    void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
  
    /// getMaxAlignment - Return the alignment in bytes that this function must be
    /// aligned to, which is greater than the default stack alignment provided by
    /// the target.
    ///
    unsigned getMaxAlignment() const { return MaxAlignment; }
  
    /// ensureMaxAlignment - Make sure the function is at least Align bytes
    /// aligned.
    void ensureMaxAlignment(unsigned Align);
  
    /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
    /// when calling another function. This is only valid during and after
    /// prolog/epilog code insertion.
    bool adjustsStack() const { return AdjustsStack; }
    void setAdjustsStack(bool V) { AdjustsStack = V; }
  
    /// hasCalls - Return true if the current function has any function calls.
    bool hasCalls() const { return HasCalls; }
    void setHasCalls(bool V) { HasCalls = V; }
  
    /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
    /// allocated for an outgoing function call.  This is only available if
    /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
    /// then only during or after prolog/epilog code insertion.
    ///
    unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
    void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
  
    /// CreateFixedObject - Create a new object at a fixed location on the stack.
    /// All fixed objects should be created before other objects are created for
    /// efficiency. By default, fixed objects are immutable. This returns an
    /// index with a negative value.
    ///
    int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable);
  
  
    /// isFixedObjectIndex - Returns true if the specified index corresponds to a
    /// fixed stack object.
    bool isFixedObjectIndex(int ObjectIdx) const {
      return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
    }
  
    /// isImmutableObjectIndex - Returns true if the specified index corresponds
    /// to an immutable object.
    bool isImmutableObjectIndex(int ObjectIdx) const {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      return Objects[ObjectIdx+NumFixedObjects].isImmutable;
    }
  
    /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
    /// to a spill slot..
    bool isSpillSlotObjectIndex(int ObjectIdx) const {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;
    }
  
    /// isDeadObjectIndex - Returns true if the specified index corresponds to
    /// a dead object.
    bool isDeadObjectIndex(int ObjectIdx) const {
      assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
             "Invalid Object Idx!");
      return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
    }
  
    /// CreateStackObject - Create a new statically sized stack object, returning
    /// a nonnegative identifier to represent it.
    ///
    int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
                          bool MayNeedSP = false, const AllocaInst *Alloca = 0);
  
    /// CreateSpillStackObject - Create a new statically sized stack object that
    /// represents a spill slot, returning a nonnegative identifier to represent
    /// it.
    ///
    int CreateSpillStackObject(uint64_t Size, unsigned Alignment);
  
    /// RemoveStackObject - Remove or mark dead a statically sized stack object.
    ///
    void RemoveStackObject(int ObjectIdx) {
      // Mark it dead.
      Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
    }
  
    /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
    /// variable sized object has been created.  This must be created whenever a
    /// variable sized object is created, whether or not the index returned is
    /// actually used.
    ///
    int CreateVariableSizedObject(unsigned Alignment);
  
    /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
    /// current function.
    const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
      return CSInfo;
    }
  
    /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
    /// callee saved information.
    void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
      CSInfo = CSI;
    }
  
    /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
    bool isCalleeSavedInfoValid() const { return CSIValid; }
  
    void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
  
    /// getPristineRegs - Return a set of physical registers that are pristine on
    /// entry to the MBB.
    ///
    /// Pristine registers hold a value that is useless to the current function,
    /// but that must be preserved - they are callee saved registers that have not
    /// been saved yet.
    ///
    /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
    /// method always returns an empty set.
    BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
  
    /// print - Used by the MachineFunction printer to print information about
    /// stack objects. Implemented in MachineFunction.cpp
    ///
    void print(const MachineFunction &MF, raw_ostream &OS) const;
  
    /// dump - Print the function to stderr.
    void dump(const MachineFunction &MF) const;
  };
  
  } // End llvm namespace
  
  #endif
  